The present invention relates to a light source device for an endoscope and, more particularly, to a light source device capable of automatically or manually adjusting an amount of light emitted from the light source device.
An object to be observed by an endoscope is generally the inside of a body cavity or a narrow tubular member. A light source device for illuminating the object is necessarily provided when using the endoscope. The light source device is designed so that the amount of its light is adjustable. The optimum amount of light for illuminating an object, so that it can be properly observed, depends on the distance from the light source device to the object. For diagnosing the body cavity by means of the endoscope, it is frequently required to take a photograph inside the coelom, which of cource is completely dark. In the endoscope photographing system, therefore, the amount of illuminating light from the light source device is varied for adjusting an exposure. This also needs the function of varying the amount of the light from the light source device. The light amount necessary for photographing a target portion is different from that for observing the target portion by the naked eye. This reason additionally requires the function of varying the amount of light from the light source device. The conventional ways to vary the light amount are, for example, to switch lamps from a lamp emitting a small amount of light to that emitting a large amount of light and vice versa, to control a current fed to a lamp, or to control a diaphragm between a lamp and an endoscope.
In the conventional light source device, it can not be known whether the light amount adjusting function of the light source device is normal or not until the light source device is actually operated. An operator may mistakenly apply to an object an endoscope which cannot adjust the light amount correctly. The result is many unavoidable problems. For example, in using medical endoscopes, there is often a case that an abnormality of the light amount adjusting function is found, after an endoscope body is inserted into the body cavity. In this case, it must be pulled out of the body cavity, repaired, and then inserted again into the body cavity. Multiple insertions of the endoscope inflicts pain on a patient which would otherwise not be caused. When photographing inside the coelom, it can be checked if the light amount adjustment functions normally after the film is developed. If it functions abnormally, the photographing must be made again. The result is an unsmooth diagnosis.